The present disclosure relates to an electrical switch, also known as a snap switch. Such an electrical snap switch is designed for selectively establishing a first conductive way between two conductive fixed contacts, or a second conductive way between two other conductive fixed contacts. The switch may include a housing, a pushbutton extending out of the housing and comprising a driving portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved relative to the housing between, a first pushbutton active position in which the first conductive way is established, and a second pushbutton active position in which the second conductive way is established.
According to a known design, a snap switch may include a conductive unit that is fixed with respect to the housing and that includes the fixed contacts, and a switching unit including a conductive swaying element, a first end of the conductive swaying element being pivotally engaged with the first conductive element, and the second end of the conductive swaying element being arranged to selectively electrically connect the first conductive fixed contact to either the second or the third conductive fixed contact, and a traction spring having a first end operatively connected to the housing and a second end secured to the swaying element, such that when the pushbutton is in the first upper pushbutton position, the spring is in a first spring position and the spring causes the swaying element to electrically connect a first pair of conductive fixed contacts, and when the pushbutton is moved to the second lower pushbutton position, the spring is moved to a second spring position and the spring causes the swaying element to also move to electrically connect a second pair of fixed contacts.
An example of such a switch is disclosed in U.S. Pat. No. 7,205,496, in which the spring is a helicoidally wounded traction spring and in which the pushbutton driving portion acts on the middle section of the spring.
An attempt to improve the working of such a snap switch is illustrated in U.S. Pat. No. 6,255,611, in which the switching unit is bistable between the first and second positions of the swaying element, in which the switch comprises a return spring that is disposed between the housing and the pushbutton, in which, when an external force applied to the pushbutton is removed, the pushbutton is returned back to its original the first active position by the return spring, and in which the traction spring has a first end connected to the driving portion of the pushbutton and a second end secured to the swaying element, so that when the pushbutton is in the first pushbutton position, the first end of the traction spring is in a first spring position, and when the pushbutton is moved to the second pushbutton position, the first end of the spring is moved to a second spring position.
According to such an arrangement, when an external force is applied to the pushbutton, the jointed end of the driving portion of the pushbutton and the elastic spring is forced to move downwards until it passes a critical line, at which point the swaying element is coupled with another conductive fixed contact to supply power or electrical signals.
According other designs disclosed in U.S. Patent Application Publication No. 2013/0068600, the swaying conductive element comprises sliding movable contacts that move in a vertical plane. The sliding contacts generate lower noises but the durability is affected due to repeated frictions between the electrical portions of contacts.
In order to improve such designs, reduce the number of components, simplify the design of the swaying conductive element, and provide with modularity concerning the number of switching conductive ways to be established or interrupted, a new design has been proposed in U.S. Patent Application Publication No. 2016/0163478, which discloses an electrical snap switch comprising a housing having a receiving portion, an actuation member in the form of a pushbutton comprising an actuating portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved vertically relative to the housing between a pushbutton upper position and a pushbutton lower position, at least a first pair of associated contact elements comprising a first fixed contact element provided in the receiving portion, and comprising a first movable contact element and that may come into contact with the first fixed contact element for establishing a first conductive way between the first movable contact element and the first fixed contact element, and a snap-action switching mechanism comprising a tilting driving member that is pivotally mounted with respect to the housing around an horizontal axis, and comprising a spring that is connected to a part of the driving member, and that cooperates with the actuating portion to move the driving member pivotally between an upper position and a lower position, the pushbutton and the tilting driving member forming a movable mechanical assembly.
Such snap switches are, for example, commonly used in the automotive industry for example for actuation of an electronic parking brake.
Consequently, there is a need to improve the reliability of operation of a snap switch of the above mentioned type, in particular to avoid discrepancies between the actuation of the switch and the actual operation of the switch.